Originally Posted by Zeful
The difference is though, you can take the sword away if it's causing trouble without inconveniencing the character for too terribly long. The spell by contrast cannot be so easily removed.
Taking equipment away permanently is a tactic of bad DM's. Whether found or purchased(or crafted), a player rightfully feels they earned that item, and it's now just as much a part of their character as their feats and spells. Taking away an item from a player for a long period of time just makes a bitter and annoyed player.
In both cases, if it's a problem, the best solution is to just talk to the player, explain the problem, and offer them something else for it.